Harvesting energy from fluid flow

ABSTRACT

The bluff body attaches to an elastic mount and is capable of generate vortex shedding when the elastic mount orients the bluff body in a flow-line traverse to a fluid flow and vibrates in response to the vortex shedding. A harvester is located within the bluff body and is capable of generating power above a specified threshold in response to the vibration.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of, and claims priorityto, U.S. patent application Ser. No. 15/608,619, entitled “HARVESTINGENERGY FROM FLUID FLOW” to inventors Talha Jamal Ahmad, MuhammadArsalan, Michael J. Black, and Mohamed Nabil Noui-Mehidi, which wasfiled on May 30, 2017. The disclosure of the foregoing application isincorporated herein by reference in its entirety.

TECHNICAL FIELD

This disclosure relates to energy harvesting from a flow-line.

BACKGROUND

In certain instances, it can be useful to generate power in a wellboreor flow-line. For example, a turbine can be placed in a wellbore orflow-line. A fluid flow through the flow-line can spin the turbine,which then turns a generator or alternator to generate power.

SUMMARY

This disclosure describes technologies relating to harvesting energyfrom fluid flow.

An example implementation of the subject matter described within thisdisclosure is an elastic bluff body with the following features. Thebluff body attaches to an elastic mount and is capable of generatevortex shedding when the elastic mount orients the bluff body in aflow-line traverse to a fluid flow and vibrates in response to thevortex shedding. A harvester is located within the bluff body and iscapable of generating power above a specified threshold in response tothe vibration.

Aspects of the example implementation, which can be combined with theexample implementation or in combination, include the following. Theharvester can vibrate at a resonance frequency of the elastic bluffbody.

Aspects of the example implementation, which can be combined with theexample implementation or in combination, include the following. Theflow-line can include a wellbore.

Aspects of the example implementation, which can be combined with theexample implementation or in combination, include the following. Thebluff body can include a cylinder.

Aspects of the example implementation, which can be combined with theexample implementation or in combination, include the following. Theharvester can include a piezoelectric harvester or a magnetostrictiveharvester.

Aspects of the example implementation, which can be combined with theexample implementation or in combination, include the following. Theharvester can include a cantilever beam configured to oscillate inresponse to the vortex shedding.

Aspects of the example implementation, which can be combined with theexample implementation or in combination, include the following. Thebluff body can include a substantially conical shape. The bluff body canpivotally connect to the elastic mount. The bluff body can oscillate inresponse to vortex shedding.

Aspects of the example implementation, which can be combined with theexample implementation or in combination, include the following. Thebluff body can include a permanent magnet and the harvester include aniron rod and a metallic coil around the iron rod.

Aspects of the example implementation, which can be combined with theexample implementation or in combination, include the following. Theharvester can include a cylinder with a metallic coil circling acircumference of the cylinder.

Aspects of the example implementation, which can be combined with theexample implementation or in combination, include the following. Theelastic bluff body can be conical and connect to the elastic mount. Theharvester can oscillate in response to the vortex shedding.

Aspects of the example implementation, which can be combined with theexample implementation or in combination, include the following. Theelastic mount can be a first elastic mount, the bluff body can be afirst bluff body, and the harvester can be a first harvester. A secondelastic mount can be separate from the first elastic mount. A secondbluff body can be attached to the second elastic mount and can generatevortex shedding when the second elastic mount orients the second bluffbody in the flow-line traverse to the fluid flow and vibrates inresponse to the vortex shedding. A second harvester can be locatedwithin the second bluff body and can generate power above a specifiedthreshold in response to the vibration.

Aspects of the example implementation, which can be combined with theexample implementation or in combination, include the following. Thesecond bluff body and the second harvester can include a substantiallyidentical natural frequency to the first bluff body and the firstharvester respectively.

An example implementation of the subject matter described within thisdisclosure is method with the following features. An oscillating vortexis induced with a bluff body and a harvester within the bluff body inresponse to flowing a fluid across the bluff body. Electrical power isgenerated in response to inducing the oscillating vortex.

Aspects of the example method, which can be combined with the examplemethod or in combination, include the following. Generating electricalpower can include vibrating a cantilever beam within the bluff body inresponse to inducing the oscillating vortex. The cantilever beam caninclude a magnetostrictive harvester or a piezoelectric harvester.

Aspects of the example method, which can be combined with the examplemethod or in combination, include the following. The bluff body caninclude a substantially conical shape. The bluff body can be pivotallyconnected to an elastic mount. The bluff body can oscillate in responseto vortex shedding.

Aspects of the example method, which can be combined with the examplemethod or in combination, include the following. The electrical powercan be stored within a battery or capacitor. A device can be powered bythe stored electrical power.

Aspects of the example method, which can be combined with the examplemethod or in combination, include the following. The device can includea sensor or communication device.

An example implementation of the subject matter described within thisdisclosure is system with the following features. A flow-line houses afluid. An elastic mount is attached to an inner surface of theflow-line. A cylindrical bluff body is attached to the elastic mount andis capable of generating vortex shedding when the elastic mount orientsthe bluff body in a flow-line traverse to a fluid flow and vibrates inresponse to the vortex shedding. A harvester is located within the bluffbody. The harvester includes a cantilever beam capable of generatingpower above a specified threshold in response to the vibration. Thecantilever beam includes a piezoelectric or magnetostrictive material. Apower rectification and conditioning circuit is coupled to thecantilever beam. An electrical storage device is coupled to the powerrectification and conditioning circuit. An electricity using device iscoupled to the electrical storage device.

Aspects of the example system, which can be combined with the examplesystem or in combination, include the following. The cylindrical bluffbody can be a first cylindrical bluff body, the harvester can a firstharvester, and the cantilever beam can be a first cantilever beam. Asecond cylindrical bluff body configured to be placed transverselywithin the flow-line, the second cylindrical bluff body can generate anoscillating vortex within the flow-line in response to a fluid flowingacross the second cylindrical bluff body. The second bluff body can bepositioned downstream and parallel of the first bluff body at a distanceappropriate for a synchronous vortex shedding mode. A second harvestercan be located within the second cylindrical bluff body. The harvestercan include a second cantilever beam that can generate power above aspecified threshold in response to the vibration. The cantilever beamcan include a piezoelectric or magnetostrictive material.

Aspects of the example system, which can be combined with the examplesystem or in combination, include the following. The power rectificationand conditioning circuit can be coupled to the second cantilever beam.

The details of one or more implementations of the subject matterdescribed in this disclosure are set forth in the accompanying drawingsand the description below. Other features, aspects, and advantages ofthe subject matter will become apparent from the description, thedrawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1B are schematic diagrams of an example bluff body in a fluidstream.

FIG. 2A is an example elastic bluff body positioned in a flow-line.

FIG. 2B is an example cantilever-beam-style harvester.

FIG. 3A is an example elastic bluff body positioned in a flow-line.

FIG. 3B is an example cantilever-beam-style harvester.

FIG. 4 is an example elastic bluff body positioned in a flow-line.

FIG. 5 is an example elastic bluff body positioned in a flow-line.

FIG. 6 is an example set of elastic bluff bodies positioned in aflow-line.

FIG. 7 is a block diagram of a power harvesting system.

FIG. 8 is a flowchart of an example method to harvest energy from afluid flow.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

The control lines used in smart completions can present an installationand maintenance challenge. The control lines are used for transmittingpower and communicating data to and from downhole equipment. The cablelengths necessary for wellbore installations can extend thousands offeet. Such lengths can incur high costs and can easily be damaged duringinstallation or maintenance operations. Inline turbines have been usedto convert mechanical energy of fluid flow through a wellbore intoelectrical energy, but turbines are mechanical systems with a shortlifespan due to their continuously moving parts. Sandy or corrosivefluid environments can shorten a turbine's usable life substantially.

This disclosure describes an elastic bluff-body configuration configuredto harvest energy from a fluid-flow induced vibration. For example, oneor more elastic bluff-body configurations can be selectively positionedand oriented within a flow-line or wellbore to harvest energy from thefluid-flow induced vibrations, for example, from 2D or 3D vortex-inducedvibrations. In some implementations, the elastic bluff-bodyconfiguration includes a bluff body configured to vibrate in response tofluid flow and a harvester coupled to the bluff body configured togenerate power in response to the fluid-flow induced vibrations. In someinstances, the bluff body can be cylindrical or conical and can bepositioned transverse to the flow-path. The bluff body can be othershapes and have other orientations without departing from the scope ofthe disclosure. In some implementations, the bluff body encloses theharvester or the harvester is located within the volume defined by theinner surface of the bluff body. The harvester can include smartmaterials (for example, piezoelectric or magnetostrictive materials) oruse induction to generate electricity. In some instances, one or moreelastic bluff body configurations can operate with power rectificationand conditioning equipment to generate usable electrical power.

In fluid dynamics, vortex shedding is an oscillating flow that occurswhen a fluid such as water or oil flows past a bluff body at asufficient velocity. In general, a higher flow velocity can produce agreater amount of power. A sufficient velocity to cause oscillations isat least partially dependent upon the size and shape of the bluff body.A bluff body can be a simple cylindrical mass. FIGS. 1A-1B illustrate aflow stream 102 flowing across a cylindrical bluff body 106 and inducinga vibration/oscillation 104. As illustrated, the bluff body 106 ispositioned transverse to the fluid flow 102. In response to the fluidflow 102, vortexes 116 are created on a downstream side of the body 106and detach periodically from either side of the body 106. This repeatingpattern of swirling vortexes 116 is also called a Kármán vortex street.Thus, flow vibrations/oscillations 104 are generated downstream of thebluff body 106 because of the vortexes 116. The vibrations/oscillations104 are also called vortex-induced vibrations, flow induced vibrations,or vortex shedding. If the bluff body 106 is flexible or flexiblymounted at a first end 110, then the oscillating vortexes 116 can causea second, unattached end 108 to oscillate between a first position 112and a second position 114. The vibrations/oscillations 104 can occurtransverse to the flow path, and can be converted into usable energy. Ifthe frequency of vortex shedding matches the resonance frequency of thestructure, the structure can begin to resonate, vibrating with harmonicoscillations driven by the energy of the flow. This phenomenon is calledlock-in.

FIGS. 2A-2B illustrate an example piezoelectric energy harvesting system200 utilizing piezoelectric material to generate power in accordancewith some aspects of the present disclosure. For example, thepiezoelectric harvesting system 200 can uses piezoelectric material togenerate electricity in response to a Kármán vortex street. In someimplementations, the piezoelectric harvesting system 200 can generateelectricity in response to irregular patterns without departing from thescope of the disclosure. As illustrated, the piezoelectric harvestingsystem 200 includes an elastic bluff-body device 201 mounted on an innersurface of the flow-line 214 and in the fluid flow 202 and is configuredto generate electricity from vortex shedding.

In this implementation, the elastic bluff body device 201 includes anelastic bluff body 206, a piezoelectric harvester 212 coupled to andlocated within the elastic bluff body 206, and an elastic mount 216 thatattaches a first end 210 of the bluff body 206 to an inner surface ofthe flow-line 214. The second end 108 of the bluff body 206 isunattached. As illustrated, the elastic bluff body 206 is orientedtransverse to the fluid flow 202. The elastic bluff body 206 can haveother orientations relative to the fluid flow 202 without departing fromthe scope of the disclosure. While the illustrated implementationutilizes a cylinder for the bluff body 206, any number of shapes can beused without departing from the scope of the disclosure. The elasticbluff body 206 can be made of PEEK, Viton, or any other materialappropriate for downhole deployment. The unattached end can be closed.In some implementations, a diameter of the elastic bluff body 206 can beten to twenty percent of the total internal diameter of the flow-line214. The bluff body 206 can generate vortex shedding when a speed of thefluid flow 202 is above a predefined threshold and vibrates in responseto the vortex shedding. For example, the bluff body 206 can oscillatetransverse to the flow 202 in response to the vortex shedding. In someimplementations, a flowrate within the flow-line 214 can be between onethousand barrels per day and six thousand barrels per day. The flowvelocity at these flowrates is dependent upon the cross-sectional areaof the flow-line 214.

Vibrations in the bluff body 206 can induce vibrations in thepiezoelectric harvester 212, and, in response to the vibrations, thepiezoelectric harvester 212 can generate power. For example, thepiezoelectric harvester 212 can generate a few hundred milli-watts ofpower or more. If a number of energy harvesters are used in acooperative manner, as described later in this disclosure, the totalamount of power depends on the total number of energy harvesters used.In the illustrated implementation, the piezoelectric harvester 212includes a cantilever beam that includes a piezoelectric material. Inthese instances, the piezoelectric material converts the cantilever'soscillations into electrical power. When the bluff body 206 vibrates ata specified threshold, the piezoelectric harvester 212 vibrates at itsresonance frequency. The resonance frequency can include a wide range offrequencies. In some implementations, the piezoelectric harvester 212can vibrate at a frequency of 10 hertz. The piezoelectric harvester 212can vibrate at frequencies above or below 10 hertz without departingfrom the scope of the disclosure. The illustrated implementation can beutilized within a wellbore, a pipeline, or any other flow-line.

In some aspects of operation, the elastic bluff body device 201 isattached or otherwise mounted to the inner surface of the flow-line 214using the elastic mount 216, and the elastic bluff-body 206 is orientedtransverse to the fluid flow 202. When the velocity of the fluid flow202 is above a predefined threshold, the elastic bluff body 206 cangenerate vortex shedding that induces vibrations in the elastic bluffbody 206. Vibrations in the elastic bluff-body 206 can induce vibrationsin the piezoelectric harvester 212. In response to the vibrations, thepiezoelectric harvester 212 can generate electricity.

FIGS. 3A-3B illustrate an example magnetostrictive harvesting system 300utilizing magnetostrictive material to generate power in accordance withsome aspects of the present disclosure. For example, themagnetostrictive material can include Galfenol, cobalt, or othermagnetostrictive materials. In general, a magnetostrictive materialchanges its magnetic field when a mechanical stress is applied on thematerial, and a coil can be used around the material to generate currentas the magnetic field changes. As a result of the changing magneticfield, the magnetostrictive harvesting system 300 can generateelectricity in response to a Kármán vortex street as well as generateelectricity in response to irregular patterns without departing from thescope of the disclosure. In contrast to the elastic bluff body device201, the piezoelectric harvester 212 is replaced with a magnetostrictiveharvester 312 and an electrical coil 318. As the flow 202 interacts withthe bluff body 206, the bluff body 206 vibrates. Vibrations in the bluffbody 206 can induce vibrations in the magnetostrictive harvester 312causing a changing magnetic flus that induces electricity in theelectrical coil 318. In some implementations, the magnetostrictiveharvester 312 can be designed such that the resonance frequency of theharvester 312 matches the oscillation frequency of the bluff body 206and increased power output can be achieved compared with otherfrequencies.

FIG. 4 illustrates a magnetic-induction harvesting system 400 utilizingmagnetic induction to generate power in accordance with some aspects ofthe present disclosure. In the illustrated implementation, themagnetic-induction harvesting system 400 uses magnetic induction togenerate power independent of moving parts such as gears or bearings.The illustrated elastic bluff-body device 401 includes a bluff body 406that is conical or tapered and an inner fixed cylinder 412 coupled tothe conical bluff body 406. The inner fixed cylinder 412 includes aniron core 413 and an electrical coil 418 wrapped around the iron core413. A first end 410 of the bluff body 406 is elastically mounted to aninner wall of the flow-line 214 using the mount 416, and the first end410 has a diameter smaller than a second end 408 of the bluff body 406.As a result of the elastic mount, the body of the bluff body 406 canmove in response to the fluid flow 202. In some conditions, the taperedor conical bluff body 206 can produce 3D oscillations as compared to 1Dthat a simple cylinder can produce in the same conditions. In theillustrated implementation, the inner cylinder 412 has a fixed diameterin contrast to the outer cylinder, i.e. the bluff body 406, that istapered or conical and hollow. The elastic bluff-body device 401 may beoriented transverse to the fluid flow 202 and 3D oscillations of theouter cylinder can occur in response to vortex shedding and lock-inphenomenon. The oscillation frequency of the bluff body 406 can, in someimplementations, match the vortex shedding frequency. The outer cylindercan be a light but ruggedized material to facilitate oscillation. Manyruggedized materials can be used, such as stainless steel, PEEK, Viton,or any other rugged material appropriate for the service.

In some aspects of operation, a magnetic field is used to convertsmechanical energy to electrical energy using a similar concept as analternator. The coil 418 attached to oscillating/rotating mass traversesa magnetic field that is established by a stationary magnet. Themagnetic flux around coil 418 changes, which induces a voltage accordingto Faraday's law. Another way is to keep the coil 418 fixed and move themagnetic structure, which can be more advantageous and can result inincreased power output. For example, the inner cylinder 412 may befixed, and the rotating bluff body 406 may produce the changing magneticfield. Moreover, the amount of electricity generated depends upon thestrength of the magnetic field, the velocity of the relative motion andthe number of turns of the coil. The magnetic field may be produced bypermanent magnets, or by a field coil electromagnet.

FIG. 5 illustrates an example magnetic-induction harvesting system 500utilizing the principles previously described in accordance with someaspects of the present disclosure. The illustrated, elastic bluff-bodydevice 501 includes a bluff body 506 that is conical or tapered and anouter fixed cylinder 512 coupled to the conical bluff body 506. Theouter fixed cylinder 512 includes an electrical coil 518 wrapped aroundthe outer circumference of the fixed cylinder 512. A first end 510 ofthe bluff body 506 is elastically mounted to an inner wall of theflow-line 214 using the mount 516, and the first end 510 has a diametersmaller than a second end 508 of the bluff body 506. As a result of theelastic mount, the body of the bluff body 506 can move in response tothe fluid flow 202. In some conditions, the tapered or conical bluffbody 206 can produce 3D oscillations as compared to 1D that a simplecylinder can produce in the same conditions. In the illustratedimplementation, the outer cylinder 512 has a fixed diameter in contrastto the inner cone, i.e. the bluff body 506, that is tapered or conical.The elastic bluff-body device 501 may be oriented transverse to thefluid flow 202. 3D oscillations of the outer cylinder can occur inresponse to vortex shedding and lock-in phenomenon. The oscillationfrequency of the bluff body 506 can, in some implementations, match thevortex shedding frequency. The outer cylinder can be a light butruggedized material to facilitate oscillation.

In some aspects of operation, a magnetic field is used to convertsmechanical energy to electrical energy using a similar concept as analternator. The coil 518 attached to oscillating/rotating mass traversesa magnetic field that is established by a stationary magnet. Themagnetic flux around coil 518 changes, which induces a voltage accordingto Faraday's law. Another way is to keep the coil 518 fixed and move themagnetic structure, which can be more advantageous and can result inincreased power output. For example, the outer cylinder 512 may befixed, and the rotating bluff body 506 may produce the changing magneticfield. Moreover, the amount of electricity generated depends upon thestrength of the magnetic field, the velocity of the relative motion andthe number of turns of the coil. The magnetic field may be produced bypermanent magnets, or by a field coil electromagnet.

FIG. 6 illustrates an example energy harvesting system 600 utilizing theprinciples previously described in accordance with some aspects of thepresent disclosure. As illustrated, the example system 600 includesmultiple bluff bodies that can be used to generate power. A firstelastic bluff body 606 a, a second elastic bluff body 606 b, and a thirdelastic bluff body 606 c are positioned substantially parallel to eachother (within standard manufacturing tolerances) within the flow-line614. The elastic bluff bodies are arranged so that they are in-line witheach other at equal distances 604 from one another. All of the bluffbodies are transverse to a flow within a flow-line 614.

In some aspects of operation, a first bluff body 606 a, a second bluffbody 606 b, and a third bluff body 606 c have substantially identicalnatural frequencies. However, one or more of the first bluff body 606 a,the second bluff body 606 b, and the third bluff body 606 c, may havedifferent natural frequencies. The distance 604 between each of thebluff bodies 606 a-c can be selected so that the vortex shedding of theprevious bluff body in the flow path induces vibrations in the followingbluff body. In other words, each bluff body can be positioned at anappropriate distance apart from one another for a synchronous vortexshedding mode to occur. Each of the elastic bluff bodies is connected tothe flow-line through an elastic mount, such as the elastic mount 216.Each of the elastic bluff bodies can include any of the implementationspreviously disclosed in this disclosure. In some implementations, themultiple bluff bodies can each include different implementations. Forexample, the first bluff-body 606 a can include the elastic bluff-bodydevice 201, the second bluff body 606 b can include the elasticbluff-body device 301, and the third bluff body 606 c can include theelastic bluff-body device 401.

In some aspects of operation, the elastic bluff bodies are attached tothe inner surface of the flow-line 614 using elastic mounts, such aselastic mount 216, and the bluff bodies are oriented transverse to thefluid flow 602. When the velocity of the fluid flow 602 is above apredefined threshold, the bluff bodies can generate vortex shedding thatproduce vibrations in the elastic bluff bodies 606 a-c. Vibrations inthe bluff bodies can induce vibrations in the harvesters 612 a-c coupledto each respective bluff body. In response to the vibrations, theharvesters can generate electricity.

A power harvesting system that harvests power from vibrations canrequire auxiliary circuitry for practical use. FIG. 7 shows a blockdiagram of an example power harvesting system 700 that can be used topower a device, such as a downhole sensor. In the illustratedimplementation, the power harvesting system 700 includes a harvester 702electrically coupled and feeds power to a rectification and conditioningcircuit 704. The harvester 702 can be any harvester that harvests powerfrom vibration, such as the piezoelectric harvester, themagnetostrictive harvester, the induction harvester, or any otherharvester previously described or capable of harvesting power fromvibration. The power rectification and conditioning circuit 704 canrectify and condition the power produced by the harvesters so that thepower can be used by a desired end device. For example, therectification and conditioning circuit 704 can convert a sporadicelectrical signal from the harvester into a low-ripple direct current.The rectified and conditioned power can then be stored within a storagedevice 706 coupled to the rectification and conditioning circuit 704,such as a battery or super capacitor. In some implementations, thestorage device 706 can be in close proximity to the harvester 702. Forexample, the harvester 702 and the storage device 706 can both belocated within the same wellbore. The power stored within the storagedevice 706 can be used to provide power to an end user device 708, suchas a downhole sensor or a downhole communication device.

FIG. 8 shows a flowchart of an example method 800 for harvesting powerfrom a fluid flow. At 802, an oscillating vortex is induced by a bluffbody and a harvester coupled to the bluff body in response to flowing afluid across the bluff body. At 803, electrical power is generated inresponse to inducing the oscillating vortex. At 804, in someimplementations, generating electrical power can include vibrating acantilever beam within the bluff body in response to the oscillatingvortex. Once the electrical power is generated, at 806, the electricalpower can be stored within a battery, a capacitor, or any otherelectrical storage device. At 808, the electrical power stored withinthe electrical storage device can power a device, such as a downholesensor, actuator, or a communication device. While the power harvestingsystem described within this disclosure is often described in thecontext of a wellbore, implementations can also exist in generalflow-lines. For example, the system could be utilized for remotepipeline condition monitoring, wireless flow metering, remote H₂Smonitoring, and any other application where harvesting power can beuseful.

While this disclosure contains many specific implementation details,these should not be construed as limitations on the scope of anydisclosures or of what can be claimed, but rather as descriptions offeatures specific to particular implementations. Certain features thatare described in this disclosure in the context of separateimplementations can also be implemented in combination in a singleimplementation. Conversely, various features that are described in thecontext of a single implementation can also be implemented in multipleimplementations separately or in any suitable subcombination. Moreover,although features can be described above as acting in certaincombinations and even initially claimed as such, one or more featuresfrom a claimed combination can in some cases be excised from thecombination, and the claimed combination can be directed to asubcombination or variation of a subcombination.

Thus, particular implementations of the subject matter have beendescribed. Other implementations are within the scope of the followingclaims. In some cases, the actions recited in the claims can beperformed in a different order and still achieve desirable results. Inaddition, the processes depicted in the accompanying figures do notnecessarily require the particular order shown, or sequential order, toachieve desirable results.

What is claimed is:
 1. An elastic bluff body, comprising: an elasticmount with a central axis; a conical bluff body with a central axis, theconical bluff body fixedly attached to the elastic mount, the centralaxis of the elastic mount and the central axis of the conical bluff bodybeing aligned, the conical bluff body being configured to generatevortex shedding when the elastic mount orients the conical bluff body ina flow-line traverse to a fluid flow and vibrates in response to thevortex shedding, wherein the conical bluff body comprises a permanentmagnet or electromagnet; and a harvester coupled to the conical bluffbody and aligned with the central axis of the conical bluff body, theharvester comprising a cylinder arranged outside of and aligned with thecentral axis of the conical bluff body, and a metallic coil circling acircumference of the cylinder, the harvester configured to generatepower above a specified threshold in response to the vibration.
 2. Theelastic bluff body of claim 1, wherein the harvester vibrates at aresonance frequency of the elastic bluff body.
 3. The elastic bluff bodyof claim 1, wherein the flow-line comprises a wellbore.